Age discrimination is real and will affect you.

Tens of thousands of workers say that even with the right qualifications for a job, they are repeatedly turned away because they are over 50, or even 40, and considered too old.

But as cases make their way to court, the legal road for proving age discrimination, always difficult, has only roughened. Recent decisions by federal appeals courts in Chicago and Atlanta have limited the reach of anti-discrimination protections and made it even harder for job applicants to win.

Workers over 50 — about 54 million Americans — are now facing much more precarious financial circumstances, a legacy of the recession.

In one of the most comprehensive studies, résumés were sent out on behalf of more than 40,000 fictitious applicants of different ages for thousands of low-skill jobs like janitors, administrative assistants and retail sales clerks in 12 cities. In general, the older they were, the fewer callbacks they got.

Those in their 60s “never do better, and often do worse,” than those a decade or two younger, said David Neumark, an economics professor at the University of California, Irvine, who oversaw the research.

It is toughest for women, who suffer more age discrimination than men starting in their 40s, the researchers found. “The evidence of age discrimination against women kind of pops out in every study,” Mr. Neumark said.